In U.S. Pat. No. 3,484,031, issued Dec. 16, 1969 to Pine, there is disclosed a stationery burster which may be manufactured to be of relatively small size and which may be placed on a table or the like for use. The Pine burster is ideally suited for stationery processing operations which do not require large bursting capacity. The Pine burster is relatively uncomplicated in terms of moving parts and drive line complexities and is adjustable to accommodate continuous business form stationery of widely varying, conventional, form lengths, typically varying from 31/2" up to 11", or more.
In the Pine burster, there is provided two sets of burster rolls, an infeed set and an outfeed set. Adjustment for varying form lengths is accomplished by varying the spacing between the two sets of rolls. The lower roll in each set is positively driven by a motor while the upper roll in each set is in idler relation to the respective lower roll and is accordingly driven thereby through frictional contact. Consequently, the roller surfaces wear and more often than not, the wear is not uniform from one end of a roll to the other. As a consequence, stationery passing along a path of stationery travel through the Pine burster, which stationery path includes roller sets, will tend to skew which in turn may interfere with proper separation of the form lengths and will frequently cause wrinkling to the extent of rendering the form unusable.
This tendency has heretofore prevented the use of trimmers in connection with the Pine burster. Trimmers are typically employed for removing margins from the continuous business form stationery and are set up at fixed locations along one or both sides of the stationery travel path. When skewing occurs, the forms tend to move to one side or the other of the stationery path with the consequence that if trimming were attempted, the line of trim, due to the fixed placement of the trimmer, would move inwardly or outwardly on the form, again rendering the form unusable.
The prior art such as depicted in U.S. Pat. No. 3,493,156, issued Feb. 3, 1970 to Absler, et al. has solved this difficulty through the use of tractor assemblies on the infeed end of a burster. Typically, the tractor assemblies will include some sort of movable means which move pins in the direction of stationery travel at the speed at which the stationery is to travel along the path. The pins positively engage the stationery by disposition in holes punched in the margins of the stationery, frequently termed control punch margins. Because of the expense of such tractor assemblies, they have heretofore been used substantially only in high capacity bursters wherein all of the burster rolls are positively driven in a precise timed arrangement such as that disclosed in U.S. Pat. No. 3,161,335, issued Dec. 15, 1964 to Pine, et al. The Pine, et al. burster is a relatively high capacity burster unlike the Pine burster and by reason of the positive driving of all burster rolls therein, is more expensive to fabricate than the Pine burster. Because all burster rolls in the Pine, et al. burster are positively driven, accommodation of a tractor unit can be readily made. When attempts have been made to place a tractor unit in a burster such as that of Pine wherein there is an idler burster roll in each set, and the drive speed of the tractor is set to be equal to that which would be applied to the stationery if positively engaged by the infeed rolls, it has been found that longer form lengths cannot be burst. Thus, the skewing problem encountered in relatively low capacity, relatively simple bursters is not susceptible to as easy a solution as merely applying a tractor to the infeed end of the burster in a conventional fashion.